Speech and voice recognition work most reliably when input speech signals are not corrupted by background noise or interfering speech signals. Signals from multiple microphones of an array of microphones may be combined to enhance a signal from a given direction, thereby reducing noise and interference from other directions. However, the direction of the speech signal to be recognized may be unknown. In addition, in a reverberant environment, sound from any given source will arrive from many directions, making source separation very difficult.